1. Introduction
This manual provides essential information for the safe and effective operation of your Nobsound NS-02D EL34-B Hi-Fi Stereo Tube Amplifier. This Class A, single-ended amplifier is designed to deliver high-fidelity audio with a warm, rich sound signature characteristic of EL34 vacuum tubes. Please read this manual thoroughly before initial use and retain it for future reference.
Image 1.1: Angled front view of the Nobsound NS-02D EL34-B Hi-Fi Stereo Tube Amplifier, showcasing its vacuum tubes and brushed metal finish.
2. Safety Information
To prevent fire, electric shock, or product damage, observe the following safety precautions:
- High Voltage: This amplifier operates with high internal voltages. Do not open the casing or attempt to service the unit yourself. Refer all servicing to qualified personnel.
- Heat: Vacuum tubes generate significant heat during operation. Ensure adequate ventilation around the amplifier. Do not place it in an enclosed space or cover ventilation openings. Avoid touching the tubes during or immediately after operation.
- Moisture: Do not expose the amplifier to rain, moisture, or excessive humidity. Keep liquids away from the unit.
- Power Source: Connect the amplifier only to a power supply of the specified voltage (240V 50Hz, as indicated on the rear panel).
- Speaker Connections: Ensure all speaker connections are secure and correct before powering on the amplifier. Incorrect connections can damage the amplifier or speakers.
- Placement: Place the amplifier on a stable, level surface away from direct sunlight, heat sources, and strong magnetic fields.
3. Setup
3.1 Unpacking and Inspection
Carefully remove the amplifier from its packaging. Inspect the unit for any signs of damage during transit. If damage is found, contact your retailer immediately.
3.2 Tube Installation (If Required)
The vacuum tubes may be pre-installed or require installation upon arrival. If installation is needed, carefully insert each tube into its corresponding socket, aligning the pins with the socket holes. Apply gentle, even pressure until the tube is seated firmly. Refer to the markings on the amplifier chassis for correct tube placement (e.g., 5Z3P, 6N9P, EL34B).
Image 3.1: Top-down view illustrating the layout of the vacuum tubes and transformers on the amplifier chassis.
3.3 Audio Input Connection
Connect your audio source (e.g., CD player, DAC, preamplifier) to the 'AUX IN' RCA jacks on the rear panel of the amplifier using high-quality RCA cables.
3.4 Speaker Connections
Connect your speakers to the appropriate speaker terminals on the rear panel. The amplifier provides terminals for both 4 Ohm and 8 Ohm speakers. Ensure you connect the positive (+) terminal of your speaker to the corresponding positive terminal on the amplifier, and the negative (-) terminal to the common ground (0) terminal. Use high-quality speaker cables.
Image 3.2: Rear panel of the amplifier, detailing the 'AUX IN' RCA jacks, speaker output terminals (4Ω, 8Ω, and common ground), and power input.
Image 3.3: Close-up view of the gold-plated speaker binding posts, showing the 4Ω, 8Ω, and common ground (0) markings for proper speaker connection.
3.5 Power Connection
After all audio and speaker connections are made, connect the supplied power cord to the amplifier's power inlet and then to a suitable wall outlet.
4. Operating Instructions
4.1 Powering On
Ensure the volume knob is set to its minimum position. Flip the 'ON/OFF' toggle switch on the front panel to the 'ON' position. The tubes will begin to glow, indicating the amplifier is warming up. Allow approximately 30-60 seconds for the tubes to stabilize before increasing the volume.
4.2 Volume Control
Slowly rotate the 'VOLUME' knob clockwise to increase the audio output. Adjust to a comfortable listening level. Avoid setting the volume to maximum for extended periods, especially with highly sensitive speakers, to prevent distortion or damage.
Image 4.1: Close-up of the front panel volume knob, indicating its minimum and maximum settings.
4.3 Powering Off
Before powering off, reduce the volume to minimum. Then, flip the 'ON/OFF' toggle switch to the 'OFF' position. Disconnect the power cord from the wall outlet if the amplifier will not be used for an extended period.
5. Maintenance
5.1 Cleaning
Dust the amplifier regularly with a soft, dry cloth. For stubborn marks, use a slightly damp cloth and then dry thoroughly. Do not use harsh chemicals or abrasive cleaners.
5.2 Ventilation
Ensure the amplifier has ample space for airflow. Do not block the ventilation holes. Proper ventilation is crucial for tube longevity and stable operation.
5.3 Tube Replacement
Vacuum tubes have a finite lifespan. Over time, their performance may degrade. If you notice a significant change in sound quality or if a tube fails, it may need replacement. Consult a qualified technician for tube replacement to ensure proper biasing and safety. Always replace tubes with compatible types (5Z3P, 6N9P, EL34B).
6. Troubleshooting
If you encounter issues with your amplifier, refer to the following common problems and solutions:
| Problem | Possible Cause | Solution |
|---|---|---|
| No sound output |
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| Distorted or weak sound |
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| Humming or buzzing noise |
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| Tubes not glowing |
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If the problem persists after attempting these solutions, please contact Nobsound customer support or a qualified audio technician.
7. Specifications
- Model: NS-02D EL34-B
- Output Power: Triode 8 W x 2 (default) / Standard Connection 12 W x 2
- Output Impedance: 4 Ω, 8 Ω
- Compatible Speakers: 10-100 W, 88 dB (or higher sensitivity)
- Rectifier Tube: 5Z3P (J-class military tube)
- Preamplifier Tubes: 6N9P × 2 (J-class military tube)
- Power Tubes: EL34B × 2
- Channels: 2.0 Stereo
- Dimensions (W x H x D): 380 x 160 x 230 mm (approximately)
- Weight: Approximately 9 kg
- Material: Tubes, Electronic Components, Metal Chassis, Wood Side Panels
- Compliance: CE
8. Warranty and Support
Nobsound products are designed for reliability and performance. For warranty information, please refer to the documentation provided at the time of purchase or contact your retailer. For technical support or service inquiries, please reach out to Nobsound customer service through their official channels.
